Xylooligosaccharides (XOS) derived from plant hemicellulose viaenzymatic hydrolysis are promising multifunctional ingredients for food applications due to their potential prebiotic, antioxidant, and sweetening properties. To develop sustainable bioprocesses for valorizing agro-industrial by-products, we assessed three recombinant xylanases from Cellulomonas sp. B6 (CsXyn10A, CsXyn10D, and CsXyn11) for their ability to release XOS from destarched wheat bran. Structural analysis by means of TLC, HPAEC-PAD, and NMR confirmed the presence of enzyme-specific linear and arabino-XOS (AXOS): CsXyn10A/D yielded mainly xylose, xylobiose, and different versions of arabino-xylotriose, while CsXyn11 generated longer (A)XOS with undetectable xylose.
A scalable charcoal-based method was used to purify crude hydrolysates (H), yielding enriched fractions (E) with around 10% xylose and up to tenfold (A)XOS concentration.
The antioxidant activity of both H and E for each enzyme was measured with the ABTS+ assay using gallic acid as a positive control; CsXyn11-derived (A)XOS showed the highest antioxidant capacity, with better results observed for CsXyn11-H than for CsXyn11-E.
The prebiotic potential of all H and E fractions was tested using Lactobacillus casei, Lactobacillus rhamnosus, and Bifidobacterium animalis in glucose-free MRS medium. All strains grew on both H and E. However, while B. animalis completely consumed A(XOS) up to DP4 in all samples, Lactobacilli showed a preference for oligosaccharides present in H over those in E. Notably, xylobiose—a mildly sweet, low-glycemic sugar—was poorly fermented when present in E.
Our results highlight the key role of enzyme selection in shaping (A)XOS structure and bioactivity. To enhance biomass valorization, we propose an integrated process that combines the enzymatic production of (A)XOS with the yeast fermentation of recovered xylose into xylitol, paving the way for clean-label, multifunctional food ingredients. Ongoing work focuses on elucidating the factors underlying the variable prebiotic potential of different (A)XOS fractions.
